• Journal of the Korean Society for Precision Engineering
• /
• v.1 no.2
• /
• pp.10-14
• /
• 1984

연삭가공은 숫돌을 구성하는 하나 하나의 입자가 공작물을 절삭하는 과정이므로 연삭현상을 이해하기 위해서는 먼저 개개 절돈의 절삭현상을 알지 않으면 안된다. 연삭입자의 절삭현상을 해명함에 있어서 기초가 되는 것은 입자와 공작물과의 간섭형상이다. 종래의 연삭 이론은 이와같은 기하학적 간섭형상이 모두 chip이 되어 제거된다(연소입자와 공작물과의 간섭 과정에서는 절삭현상만이 존재한다.)는 가정하에 연삭기구를 해석하려 하였으나 최근에 이르러 상호간섭 조건을 경계조건으로 하여 많은 사람들에 의해 연소입자의 절삭현상을 연구한 결과 연삭입자의 절삭과정은 과도적 절삭임이 밝혀졌다. 이와같은 연삭현상은 새로운 연삭이론에 기초가 될 뿐만아니라 Chip 과 표면생성기구의 관점에서도 극히 중요한 것이 된다.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05c
• /
• pp.123-130
• /
• 1996

탄소성파괴역학의 발달과 함께 원자력 발전소의 설계시 고려해야 하는 고에너지 배관의 양단파단사고와 같은 극한 가정 대신 파단전누설(LBB : Leak Before Break)개념을 배관설계시 고려할 수 있도록 관련 규제 요건이 완화되어 원자력 발전소 고에너지 계통 설계에 새로운 설계 개념으로 적용할 수 있게 되었다. 파단전누설개념 적용시 균열 안정성 평가에 가장 널리 사용되는 방법은 J-T 방법이다. 본 연구에서는 유한요소법 사용시 균열 선단에서 요소의 크기 및 경계 조건 (Boundary Condition)이 변화할 때 Applied J 적분값에 미치는 영향을 ABAQUS 전산 프로그램을 이용하여 조사하였다.

• Journal of the Korean Geotechnical Society
• /
• v.28 no.11
• /
• pp.17-31
• /
• 2012

No analytical solution exists for evaluating in-situ hydraulic conductivity of vertical cutoff walls by analyzing slug test results with consideration of transient flow. There is an analytical solution proposed to interpret a slug test performed in a partially penetrated well within an aquifer. However, this analytical solution cannot be directly applied to the cutoff wall because the solution has been developed exclusively for an infinite aquifer instead of a narrow cutoff wall. To consider the cutoff wall boundary conditions (i.e, constant head boundary and no flux boundary condition), the analytical solution has been modified in this study to take into account the narrow boundaries by introducing the imaginary well theory. Type curves are constructed from the currently derived analytical solution and compared with those of a partially penetrated well within an aquifer. The constant head boundary condition provides faster hydraulic head recovery curve than the aquifer case. On the other hand, no flux boundary condition leads to slower hydraulic head recovery. The bigger the shape factor and deviation of the well and the smaller the width of the vertical cutoff wall are, the more effect of boundary condition was observed. The type curves obtained from the analytical solution for a cutoff wall are similar to those made by the numerical method in the literature.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.16 no.5
• /
• pp.18-26
• /
• 1979

This paper extends some well-known system theories on algebraic matrix Lyapunov and Riccati equations. These extended results contain two point boundary conditions in matrix differential equations and include conventional results as special cases. Necessary and sufficient conditions are derived under which linear systems are stabilizable with feedback gains derived from periodic two-point boundary matrix differential equations. An iterative computation method for two-point boundary differential Riccati equations is given with an initial guess method. The results in this paper are related to periodic feedback controls and also to the quadratic cost problem with a discrete state penalty.

• Journal of the Korean Society of Safety
• /
• v.12 no.4
• /
• pp.220-229
• /
• 1997

The differential quadrature method (DQM) is applied to computation of the eigenvalues of the equations governing in plane and out-of-plane buckling. In-plane buckling and twist-buckling under uniformly distributed radial loads are investigated by this method. Critical loads are calculated for various end conditions and opening angles. Results are compared with existing exact solutions where available. The differential quadrature method gives good accuracy even when only a limited number of grid points is used. New results are given for two sets of boundary conditions not previously considered for this problem clamped-clamped and clamped simply supported ends.

• Journal of Korean Port Research
• /
• v.12 no.1
• /
• pp.87-93
• /
• 1998

For the calculation of the free-surface elevation, a new finite difference scheme is studied where the third derivative term for the wave elevation is artificially added in the Eulerian expression of the free-surface boundary condition. The paper presents a comparative analysis with simulations performed by the classical MAC method. More schematic computations are carried out by changing the submergence-depth and angle-of-attack. The present study shows that this new method is very efficient for the simulation of free-surface elevation around the trailing edge.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.32 no.4
• /
• pp.215-222
• /
• 2019

The heat conduction problem with discontinuous material coefficients generally consists of the conservative equation, boundary condition, and interface condition, which should be additionally satisfied in the solution procedure. This feature often makes the development of new numerical schemes difficult as it induces a layered singularity in the solution fields; thus, a special approximation is required to capture the singular behavior. In addition to the approximation, the construction of a total system of equations is challenging. In this study, a wedge function is devised for enriching the approximation, and the interface condition itself is embedded in the moving least squares(MLS) derivative approximation to consistently satisfy the interface condition. The heat conduction problem is then discretized in a strong form using the developed derivative approximation, which is named as the interface immersed MLS difference method. This method is able to efficiently provide a numerical solution for such interface problems avoiding both numerical quadrature as well as extra difference equations related to the interface condition enforcement. Numerical experiments proved that the developed numerical method was highly accurate and computationally efficient at solving the heat conduction problem with interfacial jump as well as the problem with a geometrically induced interfacial singularity.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.7 no.5
• /
• pp.73-78
• /
• 2007

It has been increasing that significant loss of life and property due to global wanning and extreme weather, and the climate and temperature changes in Korea Peninsula are now greater than the global averages. Climate information from regional climate models(RCM) at a finer resolution than that of global climate models(GCM) is required to predictclimate and weather variability, changes, and impacts. The new surface boundary conditions(SBCs) development is motivated by the limitations and inconsistencies of existing SBCs that have influence on model predictability. A critical prerequisite in constructing SBCs is that the raw data should be accurate with physical consistency across all relevant parameters and must be appropriately filled for missing data if any. The aim of this study is to construct appropriate SBCs for the RCM in Asia domain which will be used for the prevention of disasters due to climate changes. As all SBCs have constructed onto the 30km grid-mesh of the RCM suitable for Asia applications, they can be also used for other distributed models for climate and hydrologic studies.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.26 no.3
• /
• pp.282-287
• /
• 1990

In this paper, it has been analysed that the stability and the effectivity of the solution using traditional transfer matrix method. And applying the false-position method to these, the convergence characteristics of the solution has been also analysed. As a result, the frontal transfer matrix method is superior to traditional transfer matrix method in the stability and the accuracy of the solution in high frequency region but in the economical efficiency and the effectivity of the calculation, traditional transfer matrix method is more desiable. Also, it is clear that $\omega-Det$ curve using the frontal transfer matrix method is discontinuous.

• Tunnel and Underground Space
• /
• v.12 no.3
• /
• pp.142-151
• /
• 2002

Claesson(2001)'s analytical solution, and two numerical models with Dirichlet and Neuman interior boundary condition respectively were investigated to estimate the transient temperature distribution with distances from the Taejon underground food cold storage pilot cavern. Claesson's solution, which is based on constant temperature boundary condition at the rock wall during a temperature decline step, showed relatively good agreement with temperature measurements in the rock mass in order of average error difference, 0.89$\^{C}$ without any adjustments on laboratory thermal properties to represent the rock mass. For the numerical model with heat flux through the rock wall, a boundary condition setting technique was newly proposed to overcome the difficulty of prescribing variable convective heat tranfer coefficient and far-field air temperature inside the cavern as they may be certainly changed according to the cooling-down time. The results showed also good agreement with measurements in order of average error difference, 1.58$\^{C}$, and were compared to those of the numerical model with fixed temperature at the rock wall. Finally, the most proper procedure to precisely predict the temperature profile around a cavern was proposed as a series of analysis steps including an analytical exact solution and numerical models.